Perhaps that is to be expected. Airlines benefitted from a round of bankruptcy filings in the middle part of the decade. Now, despite cutting costs by significant margins, they are caught in a vicious cycle of low business travel demand, intense pricing competition for leisure passengers and rising fuel prices.

Today, shares of the seven biggest airlines are all priced in the single digits. Among the three lowest priced airlines, US Airways ( LCC) closed Thursday at $2.46, down 68% this year. United ( UAUA) closed at $3.31, down 70%. And American ( AMR) closed at $4.22, down 60%.

"Airlines are trading as if headed for bankruptcy this year," Avondale Partners analyst Bob McAdoo wrote in April, when the shares were higher than they are today.

It should be noted that at the end of the first quarter, all three carriers were holding cash. US Airways had $2.1 billion. United had $2.5 billion. American had $3.3 billion.

Nevertheless, in a recent report, Fitch analyst Bill Warlick wrote that "a bankruptcy filing by any of those (three carriers) could occur as early as the winter if operating trends fail to stabilize." The observation was included in a report last week on Delta ( DAL), which Fitch expects will "report another year of substantially negative free cash flow in 2009 as (it) struggles to adjust capacity to a diminished level of demand."

Delta's $5 billion in liquidity, and lower costs, provides the carrier with a bigger margin of safety than most of its legacy carrier competitors, Warlick wrote.